A 6mm TMT bar weighs 0.222 kg per metre, calculated with the d²/162.2 formula: (6 × 6) ÷ 162.2 = 0.222 kg/m.
A standard 12 m length of 6mm TMT weighs 2.66 kg (0.222 kg/m × 12 m).
Approximately 375 standard 12 m bars of 6mm TMT make one tonne (1,000 ÷ 2.66 kg per bar). Actual counts vary with rolling tolerance under IS 1786.